Methylcyclopentadienyl manganese tricarbonyl (hereinafter "MMT") is an antiknock agent for gasoline discovered in the fifties and sold commercially by Ethyl Corporation. It can be made by the reaction of carbon monoxide with bis(methylcyclopentadienyl) manganese referred to as "carbonylation". In this reaction, one of the methylcyclopentadienyl groups is displaced forming tars and lowering the yield of the process based on methylcyclopentadiene (hereinafter "MCP"). Attempts have been made to increase the utilization of MCP by carbonylating a methylcyclopentadienyl manganese salt rather than bis(methylcyclopentadienyl) manganese. Shapiro U.S. Pat. No. 2,916,505 describes one such attempt in which a salt such as methylcyclopentadienyl manganese chloride is mixed with a reducing agent such as sodium hydride, diethyl magnesium, triethyl aluminum and the like following which the reaction mixture is carbonylated. Using methylcyclopentadienyl manganese chloride and sodium hydride in Example I, Shapiro reports a 53% conversion of methylcyclopentadienyl manganese chloride to MMT.